The Nef Reaction
So the first photo shows the curly arrow mechanism of how the Nef reaction proceeds. The reaction is considered a bit old school these days, but who doesn’t love classic chemistry? Like nerdy vintage-ness :D
The purpose of the reaction is pretty simple: converting a mid-chain nitro group into a ketone (alkanone).
We can use a relatively weak base when extracting the proton from that chiral centre at the start. By doing this, we make certain that any other functionality within the molecule isn’t interacted with (hopefully).
It’s the use of sulfuric acid (H2SO4) that has rendered this reaction kinda obsolete. The acid is capable of decomposing the final product of the reaction. Industries are constantly looking to minimise costs and that includes maximising yields - ergo photo 2. By using ozone (O3) yield is maximised at no major cost.